How Unix searches for commands

When you type a command, Unix looks in all the directories in your search path for executable files whose name matches the command you typed.

To find out what directories are in your search path, type:
```
        echo $PATH
```
The directories are listed in the order they are searched, first to last.
To change your search path, it is necessary to edit the file that sets up the configuration of your shell (for example, file .bashrc if you use bash as your shell). See the man page for your shell for further details.
You can find out the exact path to any command by typing:
```
        which foo
```
where foo is the name of the command. For example,
```
        which bash
```
might produce the output
```
        /usr/ucb/bash
```

Next: Controlling multiple processes
See also: Unix fundamentals
Previous: How to organize large collections of files
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John Shipman, john@nmt.edu